Computer Chess Club Archives


Search

Terms

Messages

Subject: Killer moves , history heuristic , and attack table questions

Author: William Bryant

Date: 08:30:59 06/10/99


Good luck to all moderator candidates.  And now for something completely
different ...     :)

A couple of questions.

I re - de -bugged my search after adding the killer heuristic and noted
that it does better in most positions - _but_ - some positions seem to do much
worse.  I suspect this continues to be a move ordering issue.

For example,
on the endgame position FINE 70,
without the killer heuristic it fails high on ply 26 finding Kb1 in about 3 1/2
minutes, but with the killer heuristic, at about ply 20 or 21 there is a
noticable slow down in time to achieve the next ply.

Are there some positions or phases in the game where the killer moves are not
needed and should be avoided?

Is this a bug ( or feature ), and most likely due to move ordering?
If so, why apparent only after ply 20.

I noted that on this position the history heuristic begins to add up to some
larger numbers.  Is there a point where the history table should be reset or
reduced within a search rather than only at the start of each search?

Lastly, I'm thinking of adding attack tables to speed up the search.  At
present, I think they would be helpful in identifying all the squares that a
pawn or piece can attack when placed at a particular location which would speed
up the InCheck() function.  Where else would these tables be helpful?  Since I
plan to use 64 bit long long values and logical 'and' those with a square mask,
this will return a boolean value about whether the piece attacks. Can they be
used in move generation?  Other locations? Any comments, pointers, or referances
to articles or source code would be appreciated.

William
wbryant@ix.netcom.com




This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.